Metarhizium acridum

Metarhizium acridum
	Red locust with sporulating standard isolate of M. acridum
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Sordariomycetes
Order:	Hypocreales
Family:	Clavicipitaceae
Genus:	Metarhizium
Species:	M. acridum
Binomial name
	Metarhizium acridum; (Driver & Milner) J.F. Bisch., Rehner & Humber (2009)
Synonyms
	Metarhizium anisopliae var. acridum Driver & Milner

Metarhizium acridum^[1] is the new name given to a group of fungal isolates that are known to be virulent and specific to the Acrididea (grasshoppers). Previously, this species has had variety status in Metarhizium anisopliae (var. acridum^[2]); before that, reference had been made to M. flavoviride or Metarhizium sp.^[3] describing an "apparently homologous and distinctive group" of isolates that were most virulent against Schistocerca gregaria (desert locust) in early screening bioassays.

Biology

M. acridum almost exclusively infects grasshoppers (order Orthoptera): researchers believe that this has to do with the Mest1 gene which is not present in M. acridum. By taking a strain of M. robertsii that has a nonfunctioning Mest1 gene, researchers found that the mutant was only able to infect Melanoplus femurrubrum, which is consistent with M. acridum activity. This allows the initiation of the infection process on the specific targets. The expression of Mest1 in the entomopathogen M. acridum is triggered by substances that are only found on the waxy coat of the grasshoppers, which explains why this pathogen specifically only targets grasshoppers and locusts.^[4]

Applications

Biological Insecticide

M. acridum has been used to control locusts and other grasshopper pest species: originally by the international LUBILOSA programme (which developed the product Green Muscle). This team identified and addressed key technical challenges for exploitation of microbial control agents, including isolate selection, mass production, and delivery systems (formulation and application).^[5]^[6] Insect control (mortality) depends on factors such as the number of spores applied against the insect host, the formulation^[7] and weather conditions.^[8] Oil-based formulations allow the application of fungal spores under dry conditions, and are compatible with existing ultra-low volume (ULV) application techniques for locust control.

As of 2012, M. acridum was under consideration by the USDA for release in the Western U.S. for control of native grasshoppers and crickets.^[9]

Important isolates

IMI 330189 (= ARSEF 7486) is the ex-type of the species, originally collected from Niger: the active ingredient of 'Green Muscle'.
CSIRO FI 985 (= ARSEF 324) is an Australian isolate: the active ingredient of 'Green Guard'.
EVCH077 (= IMI 382977) has been isolated from an unidentified grasshopper in Benin: the active ingredient of 'NOVACRID'.

Gallery

CSIRO isolate infecting Australian plague locusts

References

^ Bischoff J.F.; Rehner S.A. & Humber R.A. (2009). "A multilocus phylogeny of the Metarhizium anisopliae lineage". Mycologia. 101 (4): 512–530. doi:10.3852/07-202. PMID 19623931. S2CID 28369561.
^ Driver, F.; Milner, R.J. & Trueman, W.H.A. (2000). "A Taxonomic revision of Metarhizium based on sequence analysis of ribosomal DNA". Mycological Research. 104 (2): 135–151. doi:10.1017/S0953756299001756.
^ Bateman, R.P.; Carey, M.; Batt, D.; Prior, C.; Abraham, Y.; Moore, D.; Jenkins, N.; Fenlon J. (1996). "Screening for virulent isolates of entomopathogenic fungi against the desert locust, Schistocerca gregaria (Forskål)". Biocontrol Science and Technology. 6 (4): 549–560. doi:10.1080/09583159631181.
^ Wang, Sibao; Fang, Weiguo; Wang, Chengshu; St Leger, Raymond J. (2011-06-23). "Insertion of an Esterase Gene into a Specific Locust Pathogen (Metarhizium acridum) Enables It to Infect Caterpillars". PLOS Pathogens. 7 (6): e1002097. doi:10.1371/journal.ppat.1002097. ISSN 1553-7374. PMC 3121873. PMID 21731492.
^ Lomer, C.J.; Bateman, R.P.; Johnson, D.L.; Langewald, J. & Thomas, M. (2001). "Biological Control of Locusts and Grasshoppers". Annual Review of Entomology. 46: 667–702. doi:10.1146/annurev.ento.46.1.667. PMID 11112183.
^ "LUBILOSA". Archived from the original on January 15, 2017. Retrieved 2021-06-12.
^ Burges, H.D., ed. (1998). Formulation of microbial biopesticides, beneficial microorganisms, nematodes and seed treatments. Dordrecht, Netherlands: Kluwer Academic. p. 412 pp. ISBN 0-412-62520-2.
^ Thomas, M.H. & Blanford, S. (2003). "Thermal biology in insect-parasite interactions". Trends in Ecology and Evolution. 18 (7): 344–350. doi:10.1016/S0169-5347(03)00069-7.
^ "Rangeland Grasshopper and Mormon Cricket Program". USDA-APHIS. Archived from the original on 9 December 2012. Retrieved 20 January 2011.